A pacing system includes a pacemaker, comprising a case which contains electronic circuitry and a power supply, and a pacing lead. A distal end of the lead interfaces with a patient's heart to deliver electrical pulses generated by the pacemaker and to provide for sensing of cardiac electrical signals. The proximal end of the lead connects to input/output terminals of the pacemaker, which are located within an external connector component of the pacemaker. A lead connector for a cardiac stimulator requires a mechanical fixation to prevent separation of the lead(s) from the pacemaker. In current commercial cardiac stimulation devices, set screws are almost universally used to accomplish such mechanical fixation. This requires additional equipment (e.g., a screwdriver) to actuate the screw. The connector assembly of the present invention utilizes a device that is easy to use and requires no additional equipment for it to work.
In a pacing system comprising a single or multiple electrode lead and a pacemaker, the distal portion of the lead holds the electrodes, which are normally placed in the right ventricle or right atrium of the heart Insulated helical coiled wire conductors connect to the electrodes to carry, along the length of the lead, physiological electrical signals from the heart to the pacemaker and pacing pulses from the pacemaker to the heart. A terminal pin is physically affixed to the proximal end of the lead, making electrical contact with the conductors within the lead The terminal pin is inserted into a socket in the connector area of the pacemaker, where the terminal pin contacts an electrical connector jack within the socket, serving as an interface between the lead conductor and electronic circuitry within the pacemaker. This connection between the terminal pin and the jack must provide for a simple, long-term safe and secure, yet detachable, connection.
The connector assembly commonly is in the form of male and female connectors, with the terminal pin at the proximal end of the pacing lead serving as the male connector. When these connectors are joined, a reliable and constant electrical contact must be maintained between the electrical conductors in the lead and the pacemaker. This connection must be secure so that the lead does not disconnect during use and is completely sealed from body fluids. However, the connection must be detachable to allow for replacement of the pacemaker or lead.
Heretofore, various connectors have been used to connect the terminal pin at the proximal end of a lead to the electrical connector jack in the socket of a pacemaker. A common connector system uses a miniature socket head set screw to secure the terminal pin to the electrical connector jack inside the socket and to provide the necessary electrical contact. When this type of connector system is employed, an implanting physician must tighten the set screw after the terminal pin of the lead is in place within the neck of the pacemaker during implantation within a patient. This procedure is difficult due to the small size of the screw and the inconvenient working conditions of the operating room. In these circumstances, the set screw may protrude into the bore of the connector socket such that it blocks the proper insertion of the pacemaker lead. Furthermore, the set screw socket or threads may be stripped due to overtightening. Another problem that may result from overtightening the screw is that the screw may bear against the outer ring of the lead termination sufficiently hard that it deforms the ring and prevents its removal from the connector socket, requiring removal of both the lead and pacemaker when replacement of the pacemaker alone would normally be desired. In addition, when an Allen wrench is inserted into the header to rotate the set screw, body fluids generally are allowed to enter the connector through the wrench seal. Furthermore, the usage of set screws is disadvantageous in that body fluids cause deterioration of a screw over time, allowing fluids to enter into the electrical contact area and resulting in circuit damage and malfunctioning.
One alternative to set screw connectors is a connector system employing various types of spring contacts in the form of small fingers which contact the lead terminal pin. The primary disadvantages of such connectors are poor mechanical contacts between leads and sockets and a suboptimal intermittent electrical contact, rather than a contact over a large surface area.
In U.S. Pat. No. 4,848,346, entitled "Pacemaker Connector System", issued to K. F. Crawford on Jul. 18, 1989, there is described a pacemaker connector system for a bipolar pacemaker, employing circular springs in each of two connector block assemblies, which circumferentially grip the central and outer terminals of a coaxial heart lead. Each of the springs has an extension arm which protrudes beyond the bounds of a pacemaker header assembly. The protruding extension arms, each of which is covered by rubber septum buttons to prevent invasion by body fluids, may be depressed to open the interior of the spring and allow insertion of the lead therein.
U.S. Pat. No. 4,942,876, entitled "Pacemaker Terminal Apparatus", issued to G. R. Gotthardt on Jul. 24, 1990, discloses a pacemaker terminal for connecting a terminal pin of a pacing lead, the terminal consisting of a two sections, a first section fixed to the pacemaker and a second section movably engaged with the first section. A spring element is interposed between the two sections to exert a force tending to displace the moveable section from the fixed section. Both sections are perforated by transverse holes which, upon application of squeezing pressure to the terminal to overcome the spring action, become aligned to allow insertion of the lead terminal pin into the holes. Upon release of the squeezing pressure, the spring element displaces the sections to capture the lead terminal pin securely in the holes. The holes may have an internal thread, for example having an asymmetric sawtooth pattern, to further hold the lead in place and maintain electrical contact.
U.S. Pat. No. 4,995,389, entitled "Multielectrode Quick Connect Cardiac Pacing Lead Connector Assembly", issued on Feb. 26, 1991 to D. L. Harris, teaches a multiple electrode lead connector assembly for connecting a plurality of insulated conductor feedthroughs, extending from a pacemaker case into a soft and pliable neck area, to a specific electrode of a multielectrode pacing lead. The connector is flexible and consists of a plurality of U-shaped spring electrical contacts, each having a bight and two upstanding legs for contacting ring contacts at the proximal end of the pacing lead. The pacemaker neck has a lumen with a closed proximal end and an open distal end which receives the multielectrode pacing lead. The upstanding legs of the U-shaped spring electrical contacts straddle the lumen of the neck in a position to flexibly engage and grip a respective ring contact on the pacing lead.
As indicated earlier, a disadvantage of connectors which employ Allen set screws to secure a pacing lead is that the aperture for entry by the wrench for turning the screw and securing the lead has a tendency to leak body fluids into the internal circuits. A further disadvantage of these connectors is the requirement for special tools and procedures for securing the lead. In a surgical clinical environment, securing a lead in this manner is highly awkward, inefficient and possibly dangerous to the patient. Similarly, although the spring contacts of the aforementioned patents avoid the necessity of special tools, they still require the surgeon to manipulate an engaging device, such as switches, buttons or levers, while securing the lead. Furthermore, these spring contacts require the surgeon to engage the lead by applying a significant insertion force. It is desirable to improve the efficiency of the implant operation by requiring less manipulation of engaging devices and the application of a smaller insertion force to engage the lead into the implantable stimulation device.
A significant disadvantage of some of the prior art connectors which employ spring contacts is their frequent inability to maintain an adequate holding force on the lead over the useful lives of the pacer and lead. Furthermore, in addition to the holding force of prior art spring contact connectors being inadequate, the insertion force required to assemble them is often inappropriately high. Accordingly, it is desirable to reduce the force of entry, or insertion force, of the terminal pin into the header jack of a spring contact connector. Moreover, it is critical to improve the holding force of connectors which employ an engaging mechanism utilizing spring contacts.
It is, therefore, a primary object of the present invention to provide a spring contact connector that requires only a low insertion force but has a high holding force.
It is another object of the present invention to provide for reliable connection of electrode leads to an implantable stimulation device, such as a pacemaker or neurostimulator, while optimizing ease of connection for the surgeon at the time of implantation, by requiring no manipulation of engaging devices or tools and by requiring minimal insertion force to engage the terminal pin of the lead with the connector jack of the implantable stimulation device.
It is a further object of the present invention to provide a connector for an implantable stimulation device which is "self-locking" in that it responds to the application of a withdrawal force on a lead by increasing its holding force upon the lead.
A still further object of the present invention is to provide the capability in a connector assembly for the electrical jack thereof to automatically secure and make electrical contact with the terminal pin of an implantable stimulation lead.
It is yet another object of the present invention to provide a connector assembly in which no tools, implements or other supporting equipment is required to release a lead from an implantable stimulation device.
A further object of the present invention is to provide a connector assembly in which no body fluid path is formed in the locking mechanism thereof.
An additional object of the present invention is to provide a connector which employs a spring contact embedded within a silicone rubber release button, or plug, which promotes stiffness and support to the spring contact, provides precise alignment of the spring within a connector housing and effectively seals the housing against intrusion of body fluids.
The connector of the present invention is a simple apparatus for lead attachment that provides the requisite mechanical and electrical connection functions, using fewer components and less labor in implementation, yet providing higher reliability, durability, resistance to breakdown due to reactions with body fluids, a small size, and efficiency in manufacture.